An Application of Wastewater Treatment in a Cold Environment and Stable Lipase Production of Antarctic Basidiomycetous Yeast Mrakia blollopis

• Published in: PLoS ONE
• Main Authors: Tsuji, Masaharu, Yokota, Yuji, Shimohara, Kodai, Kudoh, Sakae, Hoshino, Tamotsu
• Format: Text
• Language: English
• Published: Public Library of Science 2013
• Subjects: Research Article; Antarctic; East Antarctica; Naga Ike; Skarvsnes; Antarc*; Antarctica
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3597603; http://www.ncbi.nlm.nih.gov/pubmed/23516630; https://doi.org/10.1371/journal.pone.0059376

Milk fat curdle in sewage is one of the refractory materials for active sludge treatment under low temperature conditions. For the purpose of solving this problem by using a bio-remediation agent, we screened Antarctic yeasts and isolated SK-4 strain from algal mat of sediments of Naga-ike, a lake in Skarvsnes, East Antarctica. The yeast strain showed high nucleotide sequence homologies (>99.6%) to Mrakia blollopis CBS8921T in ITS and D1/D2 sequences and had two unique characteristics when applied on an active sludge; i.e., it showed a potential to use various carbon sources and to grow under vitamin-free conditions. Indeed, it showed a biochemical oxygen demand (BOD) removal rate that was 1.25-fold higher than that of the control. We considered that the improved BOD removal rate by applying SK-4 strain was based on its lipase activity and characteristics. Finally, we purified the lipase from SK-4 and found that the enzyme was quite stable under wide ranges of temperatures and pH, even in the presence of various metal ions and organic solvents. SK-4, therefore, is a promising bio-remediation agent for cleaning up unwanted milk fat curdles from dairy milk wastewater under low temperature conditions.